Human health is impacted by many microbial entities. Inoculation by viruses and bacteria cause a wide variety of sicknesses and ailments. Media attention to cases of food poisoning, strep infections, and the like is increasing public awareness of microbial issues.
It is well known that the washing of hard surfaces, food (e.g. fruit or vegetables) and skin, especially the hands, with antimicrobial or non-medicated soap, can remove many viruses and bacteria from the washed surfaces. Removal of the viruses and bacteria is due to the surfactancy of the soap and the mechanical action of the wash procedure. Therefore, it is known and recommended that the people wash frequently to reduce the spread of viruses and bacteria.
Bacteria found on the skin can be divided into two groups: resident and transient bacteria. Resident bacteria are Gram positive bacteria which are established as permanent microcolonies on the surface and outermost layers of the skin and play an important, helpful role in preventing the colonization of other, more harmful bacteria and fungi.
Transient bacteria are bacteria which are not part of the normal resident flora of the skin, but can be deposited when airborne contaminated material lands on the skin or when contaminated material is brought into physical contact with it. Transient bacteria are typically divided into two subclasses: Gram positive and Gram negative. Gram positive bacteria include pathogens such as Staphylococcus aureus, Streptococcus pyogenes and Clostridium botulinum. Gram negative bacteria include pathogens such as Salmonella, Escherichia coli, Klebsiella, Haemophilus, Pseudomonas aeruginosa, Proteus and Shigella dysenteriae. Gram negative bacteria are generally distinguished from Gram positive by an additional protective cell membrane which generally results in the Gram negative bacteria being less susceptible to topical antibacterial actives.
Antimicrobial cleansing products have been marketed in a variety of forms for some time. Forms include deodorant soaps, hard surface cleaners, and surgical disinfectants. These traditional rinse-off antimicrobial products have been formulated to provide bacteria removal during washing. The antimicrobial soaps have also been shown to provide a residual effectiveness against Gram positive bacteria, but limited residual effectiveness versus Gram negative bacteria. By residual effectiveness it is meant that bacteria growth on a surface is controlled for some period of time following the washing/rinsing process. For example, antibacterial soap, when used regularly in hand washing, has been found to provide a 1.0 log to 1.5 log reduction (i.e 90 to 97% reduction) residual effectiveness against Gram positive bacteria after two to five hours. That is skin washed with antibacterial soap, was tested two to five hours later, to be contaminated with only from 3 to 10% of the number of Gram positive bacteria compared to skin washed with a placebo soap, depending on the test protocol and bacteria tested. Also, Dial or Safeguard liquid soaps, when used in hand washing, have been found to reduce the amount of the bacteria on the skin by from about 1.5 log (97%) to about 2.5 log (99.7%) as measured by standard Health Care Personal Handwash Tests (HCPHWT). That is skin washed with these soaps were contaminated with only 0.3%-3% of the number of bacteria compared to before washing. Antimicrobial liquid cleansers are disclosed in U.S. Pat. No. 4,847,072, Bissett et al., issued Jul. 11, 1989, U.S. Pat No. 4,939,284, Degenhardt, issued Jul. 3, 1990 and U.S. Pat. No. 4,820,698, Degenhardt, issued Apr. 11, 1989, all of which are incorporated herein by reference.
Previously marketed formulations of Head & Shoulders.RTM. Dandruff Shampoo, marketed until 1994, comprised anionic surfactants, an antibacterial active and citric acid as a pH adjuster. Head & Shoulders.RTM. controlled Pityrosorum ovale fungus, which causes dandruff. PCT application WO 92/18100, Keegan et al., published Oct. 29, 1992 ("Keegan") and PCT application WO 95/32705, Fujiwara et al., published Dec. 7, 1995 ("Fujiwara") teach liquid skin cleansers comprising mild surfactants, antibacterial agents and acidic compounds to buffer the pH, which provide improved germ hostility. However, the use of the low levels of acid compounds therein, result in compositions which do not deliver the undissociated acid required to provide the improved antimicrobial benefits. This situation is compounded in Keegan and Fujiwara by the preference of mild surfactants, including nonionic surfactants.
Some of these antimicrobial products, especially the hard surface cleaners and surgical disinfectants, utilize high levels of alcohol and/or surfactants which have been shown to dry out and irritate skin tissues. Ideal personal cleansers should gently cleanse the skin, cause little or no irritation, and not leave the skin or hair overly dry after frequent use and preferably should provide a moisturizing benefit to the skin.
U.S. Pat. No. 3,141,821, issued to Compeau Jul. 21, 1964 and Irgasan DP 300 (Triclosan.RTM.) technical literature from Ciba-Giegy, Inc., "Basic Formulation for Hand Disinfection 89/42/01" set forth antibacterial skin cleansers compositions which could provide improved antimicrobial efficacy using certain anionic surfactants, antimicrobial actives and acids. However, the selection, therein, of highly active surfactants results in personal cleansing compositions which are drying and harsh to the skin.
Given the severe health impacts of Gram negative bacteria like Salmonella, Escherichia coli and Shigella, it would be highly desirable to formulate antimicrobial cleansing compositions which provide residual effectiveness versus these Gram negative bacteria, residual effectiveness versus Gram positive bacteria and improved germ reduction, and which are mild to the skin. Existing consumer products have been unable to achieve both Gram negative residual effectiveness and mildness.
Applicants have found that rinse-off antimicrobial cleansing compositions which provide such mildness and such antimicrobial effectiveness can be formulated by using known antimicrobial actives in combination with specific organic and/or inorganic acids, as proton donating agents, and specific anionic surfactants, especially a class of acidic surfactants, all of which are deposited on the skin. The deposited proton donating agent and anionic surfactant enhance the selected active, to provide a new level of hostility to bacteria contacting the skin. Use of the class of acidic surfactants has been found to give an unexpectedly high level of antimicrobial efficacy with very little impact on the mildness of the composition.